Metal drawing press



sept. 1o, 1940. w ERNST 2,214,635

METAL DRAWING PRESS Original Filed Sept. 16, .1936

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, 2,214,635 PATENT OFFICE METAL DRAWING PRESS Walter Ernst, Mount Gilead, Ohio, assignor to The Hydraulic Press Corp. Inc., Wilmin REI- Del., a corporation of Delaware Original application September No. 101,110, now Patent Divided Aug t 1, 1939.

16, 1936, Serial No. 2,167,941, dated and this application July 2, 1937, Serial No. 153,157

8 Claims. (Cl. 113-45) This invention relates to presses, and in particular, to hydraulic presses having blank-holding arrangements in association with drawing devices.

One object of this invention is to provide a hydraulic press having a drawing plunger and a plurality of clamping plungers, operating in drawing and clamping cylinders, respectively, the

pressure for operating the clamping cylinders being provided by the action of the drawing plunger in forcing the clamping plungers downwardly against the blank, means being provided for releasing' pressure fluid from the different clamping cylinders at different predetermined pressures so as to enable the blank to be held at different points by different clamping pressures.

Another object is to lprovide a hydraulic press having a drawing plunger and a plurality of clamping plungers operating in drawing and clamping cylinders, respectively, the pressure for operating the clamping cylinders being provided by the action of the drawing plunger in forcing the clamping plungers downwardly against the 25 blank, means being provided for releasing pressure fluid from the different clamping cylindersy at different predetermined pressures so as to enable the blank to 'be held at different points by different clamping pressures, the press being provided with means whereby a part of the pressure generated in the clamping cylinders is utilized to force the lclampingfmemberdownwardly, andthereby to assist the action of the drawing plunger insteadof opposing it, as in other types of presses.

Another object is to provide a hydraulic press having a drawing plunger and a plurality of clamping plungers arranged to provide diierent clamping pressures amngfthemselves, together 4 with release of pressure fluid therefrom on the attainment of different predetermined pressures therein, means being provided to prevent the escape of pressure fluid upon the return stroke of the drawing plunger when the pressure-re- 45 leasing means is set at a low amount, thereby counteracting the eifect of the pressure-releasing means during the return stroke of the press.

.This is a division of my copending application,

Ser. No. 101,110, iiled'September 16, 1936, now Patent 2,167,941, Aug. 1,1939.`

In the drawing:l

Figure 1 is a diagrammatic view, mainly in section, showing the working elements of a hydraulic press circuit arranged according to this invention, with the upper portion Aof the press framework omitted to show the construction more clearly.

Figure 2 is a horizontal section along the line 2-2 inFigure 1. e f

Figure 3 is a vertical section through a pressure relief valve employed in connection with the press circuit shown in Figure 1.

In general, the press of this invention consists of adrawing plunger and a plurality of clamping plungers having relief valves associated with each clamping plunger for release of the pressure fluid therein at predetermined pressures, thereby enabling the 4different `clamping plungers to exert different clamping pressures upon the blank. There is also provided a series of check valves adapted to prevent the individual relief valves from interfering with the action of each other, thereby preventing equalization of pressure between the different clamping cylinders by the discharges from their relief valves. The arrange- AUG 4M ment of Figure 1 also contains a provision whereby the action of the various relief valves is prevented during the return stroke by admitting uid to the opposite side of the valve plunger, this arrangement enabling the moving parts to return on the return stroke, regardless of how low the relief valve setting may be.

The reason for providing a different clamping I pressure lat different portions of the blank arises from the fact that it is found that in drawing irregular workpieces it is often desirable to hold one portion of the periphery of the blank with a tighter clamping force than other portions. In the ordinary types of presses, wherein the same clamping pressure is provided on all portions of the blank, this variable blank-holding force cannot be supplied. In the present invention, however, each individual clamping cylinder is equipped with its own relief valve and its own check valve so that a different clamping pressure can be built up on each one of the several clamping plungers.

Referring to the drawing in detail, Figure 1 shows diagrammatically a hydraulic metal drawing press having a base member III connected to a top member II (reduced in size for clearness of showing) by meansof tie rods I2; the latter being secured in position by means of the nuts I3 upon the ends thereof. Mounted in the base member I0 is a drawing die I4 having a die cavity I5 for receiving the blank I6. Associated with thefdie cavity I5 is a plunger I1 adapted to support the tip of the blank as it is being drawn, and passing through a bore IB to its operating cylinder (not shown). The details of the supporting plunger I1 form no part of the present invention, and are shown in my copending application, Ser. No. 74,742, led April 16, ,1936.

The present invention may be employedeither with fiat blanks or with blanks which have already been subjected to one or more drawing it to be drawn downwardly into the die cavity I 5. Associated with thetop member I of the press is a surge tank I9 for containing the fluid by which the press is actuated. Also associated with the top member II is the drawing or main cylinder 20, having a bore 2| within which reciprocates the double-acting drawing plunger 22 having a piston head 23 thereon. The cylinder 20 is provided with upper and lower ports 24 and 25 on opposite sides of the piston head 23, and adapted by means'of pipes 26 and 21 to supply pressure fluid to advance or retract the drawing plunger 22, according to the manner in which the fourway valve 28 is manipulated. This valve 28 is of any suitable type known to those skilled in the art, and its details form no part of the present invention.

Leading from the four-way valve 28 is the pressure line 29 connected at its opposite end to the pump 30. A discharge line 3|, also connected to the four-way valve 28,y leads into the interior of the surge tank I9. The pump 38 is also provided with a suction line 32, likewise leading into the interior of the surge tank I9. The drawing cylinder 20 is supplied near the mouth of its bore 2| with a packing ring 33, beyond which iS a packing `34adapted to be compressed by a gland 35 so as to prevent leakage around the drawing plunger 22. Connected to the drawing plunger 22 is the platen 36, within which are arranged theclamping cylinders 31 having clamping plungers 38 operating therein. Each clamping plunger 38 is provided with a. packing 39 and gland 40 for the prevention of leakage. Secured vto the platen 36 is a drawing plunger or punch 4| having a nose portion 42 corresponding to the die cavity I5, and adapted to pass through an aperture 43 in the clamping member 44 secured to the outerv ends of the clamping plungers 38.

Each'of the clamping plungers k38 is provided with a fluid passageway 45 leading by way of an outwardly opening check valve 46 to a common passageway 41, which extends upwardly through .the drawing plunger 42 and'opens into the drawing cylinder bore 2| immediately beneath the drawing plunger head 23. Consequently, uid is free to pass from the pull-back or return side of the drawing plunger 23 into the clamping cylinders 31, but is prevented from passing in the opposite direction by the action of the check valves 46. Also passing outwardly from each clamping cylinder 31 is a fluid conduit 48 leading to an intermediate portion of a pipe 49, having on one end a safety valve 50 and on the other end a pressure relief valve 5|. Leading from the dis' charge side of the safety valve 58 is a discharge line 52 connected to the discharge side of the relief valve 5| by the line 53.

The discharge line 52 passes upwardly into the telescoping Acylinder 54, thereby forming a slip connection, enabling the telescoping cylinder 54 and the pipe 52 to move vertically relatively to each other, an action which necessarily occurs when the platen 36 moves downwardlyin re- Q sponse to the action of the drawing plunger 22. A, discharge line 55 leads fom the telescoping cylinder 54 into the interior of the surge tank' I9 and serves to discharge fluid expelled from the pressure relief valve 5I of the safety valve 50. The safety'valve 58 is provided merely as an additional safety feature in the event of a jamming or other failure of the pressure relief valve 5|, and is set at a higher pressure than the relief valve 5I so as to operate in case of the accumulation of a dangerous kpressure within the correof the cap 12 past the valve plunger 62.

sponding clamping cylinder 31 and a failure of the corresponding pressure relief valve 5| to act. It Willbe seen from Figures 1 and 2 that each clamping cylinder is provided with its own pressure relief valve 5I and safety valve 50 so that a different pressure release point may be given to each clamping cylinder. The pressure relief valves 5I are connected to the drawing plunger passageway 41 by conduits 56 for the purpose of counteracting the action of the relief valves 5I during the returnv stroke of the drawing plunger 22, as is discussed below in connection with the description of the 'details of the relief valve 5|. The relief valve 5I is shown in vertical section Ain Figure 3, and consists of a casing having a bore 6I Within which reciprocates a valve plunger 62. Arranged betweenthe valvejplunger 62 and the bore 6| is a tubular member 63 hav-v ing a longitudinal bore 65 and a cross bore 66, communicating therewith vand opening into a transverse bore61 in the casing 68. The end connection of the pipe 49 is held inV communication with the bore 6I by means of the collar 68 engaging the threaded portion 69 of the casing 60, whereas the end of the pipe 53 is similarly held in communication with the transverse bore 61 by means of the threaded collar 18 engaging the threaded portion 1| of the casing (Figure 3).

Mounted on the upper portion of the'casing 60 is a tubular cap 12 secured thereto by screws 13. Within the cap 12 is a coil spring 14, one end of which engages an enlargement 15. upon the upper end of the valve plunger 62, whereas the opposite end engages a button 16 in contact with an adjusting screw 11 threaded through a bore 18 in the upper end of the cap 12; Surrounding and covering'the adjusting screw 11 justed position. 'I'he cap 12 is provided with a A port 80 receiving and communicating with the pipe 56 leading to the pull-back side o'f the drawing plunger 22, as shown in Figure 1.

Thus, when the same pressure fluid is admitted simultaneously to the valve 5I, by way of the pipes 49 and 56 during the'pull-back stroke of the press, the valve plunger 62 will be prevented from opening by means of this counteracting arrangement, as is more fully described under the operation thereof. 'I'he pipe 56 also serves during the return stroke of the press to receive and transmit the uid which leaks into the interior Thus,

each safety valve 5I may be adjusted to discharge pressure fluid at a different predetermined pressure by diierently adjusting the adjusting screw 11 to compress' the springs 14 by different amounts. The clamping member 44 is provided with rods 8| passing through the vertical bores 82 in the platen` 36, and having the nuts 83 on v the upper ends thereof. The rods 8| limit the extent to which the clamping member 44 can move relatively to the platen 36. Y

In the operation of the formof press shown in Figures 1 and 2, the pump 36 is started and delivers pressure fluid to the four-way valve 28, which in turn, is set to deliver pressure uid throughthe line 26 and port 24 into the space above the drawing plunger head 23.. 'I'his pressure forces the drawing plunger 22 and platen 36 downwardly, carrying with them theclamping member 44. When the latter engages the periphery of the blank I5 and clamps it tightly against the die member I4, the clamping member 44 halts, but the platen 36 continues to move downamaca wardly, forcing its drawing die or punch 4I into engagement with the blank I8. As the punch 4I moves downwardly it forces the central portion of the blank I6 into the die cavity I5 and overcomes the resistance of the supporting plunger I1, which protects the tip of the work-- piece or blank I6.

Meanwhile, pressure has been built up in the clamping cylinders 31 by reason of 'the relative motion`between the platen 36 and the clamping member 44 to which the clamping plungers 38 are attached, and the fluid in the clamping cylinders 31 has been prevented from escaping by the closing of the outwardly opening check valves 46. When the pressure within each clamping cylinder 31 reaches the amount for which its corresponding relief valve 5I is set, the latter opens and discharges uid through the line 53, into the discharge line 52 leadingl to the telescopicing cylinder 54, and thence by the line 55 to the surge tank I9. In this manner each clamping plunger 38 may be caused to exert a different force upon the portion of the blank periphery which is engaged by the clamping member 44 in its vicinity.

When the drawing stroke of the press has been completed the setting of the four-way valve 28 is reversed so that pressure fluid flows through the line 21 and port 25, into the space beneath the drawing plunger head 23, causing the drawing plunger 22 to move upwardly. A portion of this pressure fluid, however, passes downwardly through the plunger passageway 41, the outwardly opening relief valvesA 46, to the pasf sageways 45, into the clamping cylinders 31,

causing their plungers 38 andthe clamping member 44 to remain in clamping engagement with the blank I6 while the punch or drawing die 4I is withdrawn from the cavity I5 of the die I4. If the releif valves 5I have been set for a. low clamping pressure it would, at first glance, seem that pressure fluid during the pull-back stroke would pass from the clamping cylinders 48,

' through the relief valve 5I and lines 52, 53 and 55, back into the surge tankv I8, thus preventing the return of the moving parts. This, however, is prevented by the operation of the pipeline 56 leading from the valve cap 12 ofthe valve 5I to the passageway 41 within the drawing plunger 22. Consequently, during the pull-back stroke pressure fluid is applied simultaneously upon opposite sides of the'valve plunger 62 within the relief valve 5I, and prevents its opening regardless of how low a clamping pressure is prof vided by the setting of each relief valve 5I.

When the platen 36 has moved upwardly along the rods 8| it will engage the nuts 83 and lift the clamping member 42. free from engagement with the workpiece I6, thereby enablingfthe operator to remove the workpiece and also lifting the entire platen and blank holder assembly as a unit.

It will be understood that I desire to comprehend within this invention such modifications as come within the scope of the claims and the invention.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In combination in a drawing press, a main cylinder, a double-acting drawing plunger therein, a platen operatedl thereby, a-press bed, a workpiece 'support thereon, a plurality of clamping cylinders mounted on said platen and hydraulically connected to said main cylinder, clamping plungers'in said clamping cylinders, a clamp attached to said clamping plungers, said clamping vcylinders being responsive to the motion of said main plunger for generating pressure fluid to actuate said clamping plungers after said clamping plungers have been brought to rest by the engagement of said clamp with the workpiece on said workpiece support to clamp the workpiece during the drawing operation, and an individual pressure relief device associated with each clamping cylinder and adjustable to an individual pressure for discharging fluid from said clamping cylinder in response to the attainment of a predetermined pressure therein,.said clamping cylinders being connected with the return side of said drawing plunger for maintaining said clamping plungers in clamping engagement with the workpiece during the first part of the return stroke of. said drawing plunger, and a plurality of check valves respectively associated with said clamping cylinders for permitting the flow of fluid to said clamping cylinders from the return side of said drawing plunger but' adapted to prevent flow of fluid in the opposite direction.

2. In combination in a drawing press, a press bed, a workpiece support thereon, a drawing cylinder, a double-acting drawing plunger therein, a platen operated by said drawing plunger, clamping cylinders mounted on said platen, clamping pistons in said clamping cylinders, a clamping member attached to said clamping pistons, said clamping cylinders being responsive to the motion of said drawing plunger for generating pressure iiuid to actuate said clamping pistons after said clamping pistonsl have been brought to rest by the engagement of said clamp` ing member with the workpiece on said workpiece support, said drawing cylinder and said clamping cylinders being hydraulically interconnected by fluid-conducting means extending from the return side of said drawing cylinder, to said clamping cylinders for conveying fluid therebetween, a pressurerelief device connected to each clamping cylinder for discharging pressure therefrom in response tothe attainment of a predetermined pressure therein, and means connecting said pressure relief devices to the return side of said drawing cylinder for rendering said pressure relief devices inoperative during the return stroke of said drawing plunger.

. 3. In combination in a drawing press, a press bed, a workpiece support thereon, a drawing cylinder, a double-acting drawing plunger therein, a platen operated by said drawing plunger, clamping cylinders mounted on said platen, clamping pistons in said clamping cylinders, a clamping member attached to said clamping pistons, said clamping cylinders being responsive to the motion of said drawing plunger for generating pressure fluid to actuate said clampingv pistons after said clamping pistons have been brought to rest by the engagement of said clamping member vwith the workpiece on said workpiece support, said drawing cylinder and said clamping cylinders being hydraulically interconnected by' duid-conducting means extending from the return side of said drawing cylinder to said clamping cylinders for conveying uid therebetween, a pressure relief device connected to -each clamping cylinder for discharging pressure pressure relief devices inoperative during the return stroke of said'drawing plunger, and unidirectional valve means associated with the fluid-conducting means for permitting the ow of fluid to said clamping cylinder from the return side of said drawing plunger but adapted to prevent the flow'of iluid in the opposite direction to maintain the clamping action of the clamping plungers during the return stroke of said drawing plungers.

4. In combination in a drawing press, a drawing cylinder, a double-acting drawing plunger therein, a platen operated by said drawing plunger, a plurality of clamping cylinders in said platen, clamping plungers in said clamping cylinders, a clamping member attached to said clamp ing plungers and adapted to be operated by the relative motion between said clamping cylinders,

and said clamping plungers, a plurality of pressure relief valves adjustable to different releasing pressures, one pressure relief valve being connected to each clamping cylinder for discharging pressure uid thereofrom in response to the attainment of a predetermined pressure therein, fluid passageways interconnecting said clamping cylinders and the return side of said drawing plunger for conveying fluid to said clamping cylinders to maintain the clamping action of the clamping plungers and hold the clamping members in 'engagement with the workpiece at the start of the return stroke of the drawing plunger and a plurality of check valves respectively provided in said uid passageways and associated with said clamping cylinders for pers, mitting the ow of fluid to said clamping cylinders from the return side of said drawing plung` er-but adapted to prevent flow of uid in the opposite direction.

5. In combination in a drawing press, a drawing cylinder, a double-acting drawing plunger therein, a platen operated by said drawing plunger, a plurality of clamping cylinders in said platen, clamping plungers in said yclamping'cylinders, a clamping member attached to said clamping plungers and adapted to be operated by the relative motion between said clamping cylinders and said clamping plungers, a' plurality of pressure relief valves adjustable to different releasing pressures, one pressure relief valve being connected to each clamping cylinder for discharging pressure fluid therefrom in response to the attainment of a predetermined pressure therein, fluid passageways intercomneeting said clamping cylinders and the return side of said drawing plunger for conveying fluid to' said clamping cylinders to maintain the clamping action of the clamping plungers and hold the clamping member in engagement with the workpiece at the start of th'e return stroke of the drawing plunger, and check valves in each of the respective passageways for preventing the flow of fluid from said clamping cylinders to the return side of said drawing plunger.

6. In combination in a drawing press, a main cylinder, a main plunger, a platen operated thereby, a press bed, a workpiece support thereon, a plurality of clamping cylinders mounted on said platen, clamping plungers operating therein, a clamp attached to said clamping plungers, said clamping cylinders being hydraulically connected to the return side of said main cylinder whereby to maintain the clamp in engagement with pressure differing from the discharge pressure in at least one of the .other clamping cylinders, and means interconnecting said pressurerelief valves with the return side of said main plunger for rendering said pressure relief valves inoperative during the return stroke of said main plunger.

7. In combination in a drawing press, a main cylinder, a main plunger, a platen operated thereby, a press bed, a workpiece support thereon, a plurality of clamping cylinders mounted on said platen, clamping plungers operating therein, a clamp attached to said clamping plungers, said clamping cylinders being hydraulically connected to the return side of said main cylinder whereby to maintain the clamp in engagement with the workpiece during the first part of the return stroke of said main plunger, said clamping cylinders being responsive to the motion of said main plunger for generating pressure uid to actuate said clamping plungers after said clamping plungers have been brought to rest by the engagement of said clamp with the workpiece on said workpiece support, an adjustable pressure relief valve for each clamping cylinder arranged to discharge pressure iluid individually from each clamping cylinder' at a predetermined pressure diering from the discharge pressure in atleast lone of the other clamping cylinders, and a conduit extending from said pressure relief valves to the return side of said main plunger, said pressure relief valves including means for rendering said pressure relief valves inoperative during the return stroke of said main plungers.

8. In combination in a drawing press, a press bed, a workpiece support thereon, a drawing cylinder, a double-acting drawing plunger there'- in, a platen operated by said drawing plunger, clamping cylinders mounted on said platen, clamping pistons in said clamping cylinders, a clamping member attached to -said clamping pistons, said clamping cylinders being hydraulically connected to the return side of said drawing cylinder whereby to maintain the clamp in engagement with the workpiece .during the rst part of the return stroke of said drawing plunger, said clamping cylinders being responsive to the motion of said drawing plunger for generating pressure fluid to actuate said clamping pistons after said clamping pistons have been brought tov rest by the engagement of said clamping member with the workpiece on said workpiece support, a pressurerelief device connected to each clamping cylinder for discharging pressure therefrom in response to the attainment of a. predetermined pressure therein, and means connecting said pressure relief devices to the return side of said drawing cylinder for rendering said pressure relief devices inoperative during the return stroke of said drawing plunger.

, WALTER ERNST. 

